Method for communicating with data through component carriers in mobile communication system to which carrier aggregation method is applied and apparatus therefor

ABSTRACT

The present invention relates to a method for enabling a terminal to communicate with data by modifying an association relationship among component carriers in a mobile communication system supporting carrier aggregation and an apparatus therefor. The method in accordance with one embodiment of the present invention, comprises: receiving a message including identifier information for modifying an association relationship among at least one downlink component carrier and at least one uplink component carrier from a base station; receiving predetermined data through at least one downlink component carrier from the base station; and transmitting feedback data to the base station for data received through the uplink component carrier modified according to the identifier information.

TECHNICAL FIELD

The present invention relates to a method for a user equipment tocommunicate data by modifying a connection relation between componentcarriers in a mobile communication system to which a carrier aggregationscheme is applied and a user equipment for the same.

BACKGROUND ART

The standard of LTE-A technology, which is a candidate IMT-Advancedtechnology of the International Telecommunication Union (ITU), has beendesigned to meet the requirements of the IMT-Advanced technology of theITU. In the LTE-A system, Carrier Aggregation (CA) technology, whichaggregates and uses a plurality of component carriers each of which maybe used as a carrier in the existing LTE system, is being discussed toextend bandwidth.

If a plurality of downlink component carriers and/or a plurality ofuplink component carriers are configured for one UE, there may be aproblem associated with connection relations between the componentcarriers unlike when a downlink component carrier and an uplinkcomponent carrier are configured for one UE.

That is, if connection relations between downlink component carriers anduplink component carriers are indefinitely established, it will bedifficult to determine an uplink component carrier through whichfeedback information for data received through a downlink componentcarrier is to be transmitted.

In addition, when a new component carrier different from pre-setcomponent carriers is added, there may also be a problem associated witha connection relation established for communication of data through theadded component carrier and therefore there is a need to provide asolution to such a problem.

DISCLOSURE Technical Problem

In view of the above need, an object of the present invention is toprovide a method for a user equipment to communicate data by modifying aconnection relation between component carriers in a mobile communicationsystem to which a carrier aggregation scheme is applied and a userequipment for the same.

Technical Solution

To accomplish the above object, one aspect of the present inventionsuggests a method for a user equipment to communicate data by modifyinga connection relation between component carriers in a mobilecommunication system to which a carrier aggregation scheme is applied,the method including receiving a message including identifierinformation that modifies a connection relation between at least onedownlink component carrier and at least one uplink component carrierfrom a base station, receiving data from the base station through one ofthe at least one downlink component carrier, and transmitting feedbackdata for the received data to the base station through an uplinkcomponent carrier modified based on the identifier information.

Here, the message may further include information for addition of afirst downlink component carrier, and the identifier information mayinclude information for configuration of a connection relation betweenthe added first downlink component carrier and one of the at least oneuplink component carrier.

In addition, the message may further include information for removal ofa second downlink component carrier among the at least one downlinkcomponent carrier, and the identifier information may includeinformation for configuration of a connection relation between one ofthe at least one downlink component carrier other than the seconddownlink component carrier to be removed and an uplink component carrierconnected to the second downlink component carrier to be removed.

Further, the message may further include information for addition of afirst uplink component carrier, and the identifier information mayinclude information for configuration of a connection relation betweenthe added first uplink component carrier and one of the at least onedownlink component carrier.

Furthermore, the message may further include information for removal ofa second uplink component carrier among the at least one uplinkcomponent carrier, and the identifier information may includeinformation for configuration of a connection relation between one ofthe at least one uplink component carrier other than the second uplinkcomponent carrier to be removed and a downlink component carrierconnected to the second uplink component carrier to be removed.

Advantageous Effects

According to the embodiments of the present invention described above,it is possible to efficiently change a connection relation betweencomponent carriers for data communication through a message in a mobilecommunication system that uses a carrier aggregation scheme while it ispossible to easily configure a new connection relation throughidentifier information included in a message.

DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a network structure of an Evolved UniversalTerrestrial Radio Access Network (E-UTRAN) as an example of a mobilecommunication system;

FIGS. 2 and 3 illustrate a radio interface protocol between a UE and anE-UTRAN based on the 3GPP wireless access network standard;

FIG. 4 illustrates operations associated with radio link failure;

FIGS. 5 and 6 illustrate the case in which an RRC connectionre-establishment procedure is successful and the case in which an RRCconnection re-establishment procedure has failed;

FIG. 7 illustrates carrier aggregation technology that is applied to a3GPP LTE-A system;

FIGS. 8A-8B illustrate an exemplary connection relation between a singleCC and a single CC according to system information in a carrieraggregation scheme and exemplary addition of a downlink CC;

FIG. 9 illustrates an example in which connection relations between CCsare changed through identifier information;

FIG. 10 illustrates an example in which a downlink CC is added and a newconnection relation is configured;

FIG. 11 illustrates an example in which an existing downlink CC isremoved and a new connection relation is configured;

FIG. 12 illustrates an example in which an uplink CC is added and a newconnection relation is configured;

FIG. 13 illustrates an example in which an uplink CC is added and aconnection relation between the added uplink CC and an existing downlinkCC is configured;

FIG. 14 illustrates an example in which an existing uplink CC is removedand a new connection relation is configured;

FIG. 15 illustrates an example in which a downlink CC and an uplink CCare added and a new connection relation is configured;

FIG. 16 illustrates an example in which a downlink CC is added, anexisting uplink CC is removed, and a new connection relation isconfigured;

FIG. 17 illustrates an example in which a downlink CC is removed, anexisting uplink CC is added, and a new connection relation isconfigured;

FIG. 18 illustrates an example in which an existing downlink CC and anexisting uplink CC are removed and a new connection relation isconfigured;

FIG. 19A illustrates a contention-based random access procedure to whichthe present invention may be applied;

FIG. 19B illustrates a non-contention-based random access procedure towhich the present invention may be applied;

FIG. 20 illustrates a configuration of an embodiment of a wirelesscommunication system including a UE and an eNB according to the presentinvention;

FIG. 21 illustrates functions (especially, associated with a structureof an L2 (second) layer) of the processor of the eNB to which theembodiments of the present invention are applied; and

FIG. 22 illustrates functions (especially, associated with a structureof an L2 (second) layer) of the processor of the UE to which theembodiments of the present invention are applied.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention with reference to the accompanying drawings. Thedetailed description, which will be given below with reference to theaccompanying drawings, is intended to explain exemplary embodiments ofthe present invention, rather than to show the only embodiments that canbe implemented according to the invention. For example, although thepresent invention will be described with reference to a 3GPP LTE basedsystem as an example of a mobile communication system, the presentinvention may be applicable in various ways as a method for a UE toperform power-efficient measurement in various mobile communicationsystems, such as an IEEE 802.16 based system, to which carrieraggregation technology is applicable.

The following detailed description includes specific details in order toprovide a thorough understanding of the present invention. However, itwill be apparent to those skilled in the art that the present inventionmay be practiced without such specific details. In some cases, knownstructures and devices are omitted or shown in block diagram form,focusing on important features of the structures and devices, so as notto obscure the concept of the present invention. The same referencenumbers will be used throughout this specification to refer to the sameor similar elements.

A method for power-efficiently performing channel quality measurement ina mobile communication system which uses a carrier aggregation scheme asdescribed above and a UE for the same will be described below. To thisend, first, a 3GPP LTE system is briefly described as an example of amobile communication system to which the present technology may beapplied.

FIG. 1 illustrates a network structure of an Evolved UniversalTerrestrial Radio Access Network (E-UTRAN) as an example of a mobilecommunication system. The E-UTRAN system is an evolved version of theconventional UTRAN system and the basic standardization thereof iscurrently underway in the 3GPP. The E-UTRAN system is also referred toas a Long Term Evolution (LTE) system.

The E-UTRAN includes e-NodeBs (eNBs or base stations) and eNBs areconnected through X2 interfaces. An eNB is connected to a User Equipment(UE) through a radio interface and is connected to an Evolved PacketCore (EPC) through an Si interface.

The EPC includes a Mobile Management Entity (MME), a Serving-Gateway(S-GW), and a Packet Data Network-Gateway (PDN-GW). The MME contains UEaccess information or information associated with UE capabilities. Suchinformation is mainly used for UE mobility management. The S-GW is agateway whose end point is the E-UTRAN and the PDN-GW is a gateway whoseend point is the PDN.

Layers of Radio Interface Protocol between a UE and a network may beclassified into an L1 layer (first layer), an L2 layer (second layer),and an L3 layer (third layer) based on the lower 3 layers of the OpenSystem Interconnection (OSI) reference model that is widely known incommunication systems. A physical layer which belongs to the first layerprovides an information transfer service using a physical channel and aRadio Resource Control (RRC) layer located at the third layer serves tocontrol radio resources between the UE and the network. To accomplishthis, the RRC layer exchanges RRC messages between the UE and an eNB.

FIGS. 2 and 3 illustrate a radio interface protocol between a UE and anE-UTRAN based on the 3GPP wireless access network standard.

The radio interface protocol is horizontally divided into a physicallayer, a data link layer, and a network layer and is vertically dividedinto a user plane (U-plane) for data/information transfer and a controlplane (C-plane) for control signal (signaling information) transfer. Theprotocol layers of FIGS. 2 and 3 may be classified into an L1 layer(first layer), an L2 layer (second layer), and an L3 layer (third layer)based on the lower 3 layers of the Open System Interconnection (OSI)reference model that is widely known in communication systems. Suchradio protocol layers are provided in pairs in the UE and the E-UTRANand are responsible for data transmission in radio intervals.

The layers of the radio protocol control plane of FIG. 3 and the radioprotocol user plane of FIG. 3 are described below.

The physical layer of the first layer provides an information transferservice to higher layers using a physical channel. The physical layer isconnected to the Media Access Control (MAC) layer, which is locatedabove the physical layer, through a transport channel. Data is deliveredbetween the MAC layer and the physical layer through the transportchannel. Data is delivered between different physical layers, i.e.,between physical layers of transmitting and receiving sides, through aphysical channel. The physical channel is modulated according to anOrthogonal Frequency Division Multiplexing (OFDM) scheme and utilizestime and frequency as radio resources.

A MAC layer of the second layer provides a service to a Radio LinkControl (RLC) layer, which is located above the MAC layer, through alogical channel. The RLC layer of the second layer supports reliabledata transmission. The functionality of the RLC layer may be implementedas a functional block within the MAC layer. In this case, the RLC layermay be absent. A PDCP layer of the second layer performs a headercompression function to reduce the size of an IP packet header thatcontains relatively large and unnecessary control information in orderto achieve efficient transmission in a small-bandwidth radio intervalwhen transmitting an IP packet such as an IPv4 or IPv6 packet.

A Radio Resource Control (RRC) layer located at the bottom of the thirdlayer is defined only in the control plane and is responsible forcontrol of logical channels, transport channels, and physical channelsin association with configuration, re-configuration, and release ofRadio Bearers (RBs). Here, the term “RB” refers to a service that isprovided by the second layer for data transfer between a UE and a UTRAN.The UE is in an RRC_CONNECTED state when there is an RRC connectionbetween an RRC layer of the UE and an RRC layer of a wireless networkand is in an RRC_IDLE state when there is no RRC connection.

Downlink transport channels which transmit data from a network to a UEinclude Broadcast Channel (BCH) that transmits system information anddownlink Shared Channel (SCH) that transmits user traffic or controlmessages. Traffic or control messages of downlink multicast or broadcastservice may be transmitted through downlink SCH or may be transmittedthrough downlink Multicast Channel (MCH). Uplink transport channels thattransmit data from a UE to a network include Random Access Channel(RACH) that transmits initial control messages and uplink SCH thattransmits user traffic or control messages.

Logical channels, which are located above transport channels and aremapped thereto, include Broadcast Channel (BCCH), Paging Control Channel(PCCH), Common Control Channel (CCCH), Multicast Control Channel (MCCH),and Multicast Traffic Channel (MTCH).

A physical layer includes a plurality of subframes in the time axis anda plurality of subcarriers in the frequency axis. One subframe includesa plurality of symbols in the time axis. One subframe includes aplurality of resource blocks, each of which includes a plurality ofsymbols and a plurality of subcarriers. Each subframe may use specificsubcarriers of specific symbols (for example, the first symbol) in thesubframe for a Physical Downlink Control Channel (PDCCH), i.e., an L1/L2control channel. One subframe may include 2 slots, each having a lengthof 0.5 ms, and one subframe may correspond to a Transmission TimeInterval (TTI) of 1 ms which is a unit time for transmitting data.

The following is a description of system information. System informationincludes essential information that a UE should know to access an eNB.Accordingly, the UE should receive all system information beforeaccessing the eNB and the system information received by the UE shouldalways be the latest system information. Since all UEs in one cellshould acquire the system information, the eNB transmits the systeminformation periodically.

The system information is divided into a Master Information Block (MIB),a Scheduling Block (SB), and a System Information Block (SIB). The MIBallows the UE to know a physical configuration (for example, bandwidth)of the corresponding cell. The SB notifies the UE of transmissioninformation (for example, transmission period) of SIBs. The SIB is a setof related system information. For example, one SIB includes informationof only adjacent cell(s) while another SIB includes information of onlyuplink radio channel(s) used by the UE.

Services that the network provides to the UE may be classified into 3types. The UE identifies the type of a cell differently according towhich services the UE can receive from the cell. First, the servicetypes are described as follows and then the types of the cell aredescribed.

1) Limited service: This service provides an emergency call and an ETWSand can be provided by an acceptable cell.

2) Normal service: This is a general service for public use and can beprovided by a suitable cell.

3) Operator service: This is a service for a communication networkprovider and the corresponding cell can be used only by thecommunication network provider and cannot be used by general users.

The types of cells can be classified as follows in association with thetypes of services provided by the cells.

1) Acceptable cell: This is a cell in which a limited service can beprovided for the UE. This cell is not barred for the UE and satisfiescell selection criteria for the UE.

2) Suitable cell: This is a cell in which a normal service can beprovided for the UE. This cell satisfies acceptable cell conditionswhile satisfying additional conditions. The additional conditionsinclude a condition that the cell belongs to a PLMN that can be accessedby the UE and a condition that, in the cell, the UE is not prohibitedfrom performing a tracking area update procedure. If the cell is a CSGcell, it is required that the UE be able to access the cell as a CSGmember.

3) Barred cell: This is a cell that broadcasts information indicatingthat it is a barred cell through system information.

4) Reserved cell: This is a cell that broadcasts information indicatingthat it is a reserved cell through system information.

An RRC state and RRC connection method of a UE are described below. TheRRC state indicates whether or not an RRC layer of the UE is logicallyconnected to an RRC layer of the E-UTRAN. It is stated that the UE is inan RRC_CONNECTED state when there is a logical connection between theRRC layer of the UE and the RRC layer of the E-UTRAN and it is statedthat the UE is in an RRC_IDLE state when there is no logical connectiontherebetween. When the UE is in an RRC_CONNECTED state, the E-UTRAN candetermine presence or absence of the UE on a cell basis since there isan RRC connection between the UE and the E-UTRAN and therefore caneasily control the UE. On the other hand, the UE is in an RRC_IDLE statecannot be identified by the E-UTRAN, and can be managed by a corenetwork on the basis of a tracking area which is an area unit greaterthan the cell. That is, when the UE is in an RRC_IDLE state, only thepresence or absence of the UE is identified on a large area basis andthe UE needs to shift to an RRC_CONNECTED state in order to receive anormal mobile communication service such as a voice or data service.

When the user initially powers the UE on, first, the UE searches for anappropriate cell and then remains in an RRC_IDLE state in the cell. Whenthe UE needs to establish an RRC connection while the UE remains in anRRC_IDLE state, the UE shifts to an RRC_CONNECTED state by establishingan RRC connection with the E-UTRAN through an RRC connection procedure.In various cases, there may be a need to establish an RRC connectionwhile the UE is in an idle state. For example, the UE may need toestablish an RRC connection when there is a need to transmit uplink databecause of the user's attempt to call or when there is a need totransmit a response message in response to a paging message receivedfrom the E-UTRAN.

A Non-Access Stratum (NAS) layer which is located above the RRC layerperforms functions such as session management and mobility management.

In the NAS layer, two states, an EPS Mobility Management-registered(EMM-REGISTERED) state and an EMM-DEREGISTERED state, are defined inorder to manage mobility of the UE. These two states are applied to theUE and the MME. Initially, the UE is in an EMM-DEREGISTERED state. Here,the UE performs a procedure for registering the UE in a network throughan initial attach procedure in order to access the network. When theattach procedure has been successfully performed, the UE and the MMEenter an EMM-REGISTERED state.

Two states, an EPS Connection Management (ECM)-IDLE state and anECM-CONNECTED state, are defined in order to manage signaling connectionbetween the UE and the EPC. These two states are applied to the UE andthe MME. If the UE establishes an RRC connection with the E-UTRAN whenthe UE is in an ECM-IDLE state, the UE enters an ECM-CONNECTED state. Ifthe MME establishes an Si connection with the E-UTRAN when the MME is inan ECM-IDLE state, the MME enters an ECM-CONNECTED state. When the UE isin an ECM-IDLE state, the E-UTRAN does not have context information ofthe UE. Therefore, the UE performs a UE-based mobility related proceduresuch as cell selection or reselection without the need to receive acommand from the network. On the other hand, when the UE is in anECM-CONNECTED state, mobility of the UE is managed by a command from thenetwork. When the position of the UE has changed from that known by thenetwork while the UE is in an ECM-IDLE state, the UE notifies thenetwork of the changed position of the UE through a tracking area updateprocedure.

The following is a description of a radio link failure procedure in a3GPP LTE system.

A UE constantly performs measurement in order to maintain the quality ofa communication link with a cell which currently provides a service tothe UE. Specifically, the UE determines whether or not the quality ofthe communication link with the cell that currently provides a serviceto the UE is bad to the extent that communication is impossible. Upondetermining that the quality of the communication link is bad to theextent that communication is impossible, the UE declares radio linkfailure. If the UE declares radio link failure, the UE gives up keepingthe communication with the cell and then attempts RRC connectionre-establishment after selecting a cell through a cell selectionprocedure. Operations associated with such radio link failure may beperformed in two steps as shown in FIG. 4.

In the first step, the UE checks if there is a problem in the currentcommunication link. If there is a problem, the UE declares a radio linkproblem and awaits recovery of the communication link for apredetermined time of T1. If the link is recovered within the time T1,the UE continues normal operation. If the radio link problem is notsolved within the time T1, the UE declares radio link failure and entersthe second step. In the second step, the UE performs an RRC connectionre-establishment procedure for recovery from the radio link failure.

The RRC connection re-establishment procedure is a procedure forre-establishing an RRC connection in an RRC_CONNECTED state. The UE doesnot initialize all radio configuration (for example, radio bearerconfiguration) of the UE since the UE remains in an RRC_CONNECTED state,i.e., since the UE does not enter an RRC_IDLE state. Instead, the UEsuspends use of all radio bearers excluding SRB0 when starting the RRCconnection re-establishment procedure. If RRC connectionre-establishment is successful, the UE resumes using the radio bearers,the use of which has been suspended.

FIGS. 5 and 6 illustrate the case in which an RRC connectionre-establishment procedure is successful and the case in which an RRCconnection re-establishment procedure has failed.

How a UE operates in the RRC connection re-establishment procedure isdescribed below with reference to FIGS. 5 and 6. First, the UE performsa cell selection procedure to select one cell. The UE receives systeminformation in order to receive basic parameters for cell access fromthe selected cell. Then, the UE attempts RRC connection re-establishmentthrough a random access procedure. When the cell that the UE hasselected through cell selection is a cell (i.e., a prepared cell) whichhas context of the UE, the cell can accept the RRC connectionre-establishment request of the UE, resulting in that the RRC connectionre-establishment procedure is successful. However, when the cellselected by the UE is not a prepared cell, the cell cannot accept theRRC connection re-establishment request of the UE since the cell has nocontext of the UE, resulting in failure of the RRC connectionre-establishment procedure.

FIG. 7 illustrates carrier aggregation technology that is applicable toa 3GPP LTE-A system.

The standard of LTE-A technology, which is a candidate IMT-Advancedtechnology of the International Telecommunication Union (ITU), has beendesigned to meet the requirements of the IMT-Advanced technology of theITU. Accordingly, it is being discussed that LTE-A system bandwidth isextended compared to the existing LTE system bandwidth in order tosatisfy the requirements of the ITU. To extend the bandwidth in theLTE-A system, it is being discussed that carriers that may be used inthe existing LTE system are defined as component carriers (CCs) and thedefined CCs are used in groups, each including up to 5 CCs. Since eachCC may have a bandwidth of up to 20 MHz as in the LTE system, thebandwidth can be extended up to 100 MHz. Such technology for using CCsin groups, each including a plurality of CCs, is referred to as CarrierAggregation (CA).

To use CCs, the UE needs to receive configuration information of CCsfrom an eNB. The CC configuration information may include at least partof CC system information and/or parameter values associated withrespective operations of CCs. Upon receiving the CC configurationinformation from the eNB, the UE can transmit and receive data througheach CC.

As described above, in the LTE-A system, a plurality of CCs can beconfigured and the configuration of the plurality of CCs may be modifiedor the configuration may be changed such that a new CC is added to theplurality of CCs or a CC is removed from the plurality of CCs.

Such a change can be made through an RRC connection re-establishmentprocedure. For example, to add a new CC to a plurality of CCs configuredfor a UE, the network may transmit, to the UE, an RRC connectionre-establishment message including configuration information of theplurality of CCs required to run a new CC that is to be added to theplurality of CCs for the UE and the UE may configure a plurality of CCsby adding the new CC using the received CC configuration information.

For example, the eNB may modify CCs through a message structure as shownin the following table.

TABLE 1 Level n + Level n + Level n + Level-n IE k IE k + 1 IE k + 2 IEAdd CC, CC Identification DL CC DL CC specific Modify CC, Information,configuration configuration IE CC configuration . . . . . . UL FeedbackCC identifier UL CC UL CC specific configuration configuration IE(OPTIONAL) . . . . . . DL Feedback CC identifier Release CC CCidentifier, Release Indicator {UL CC only release, DL CC only release,UL and DL CC release}

Table 1 is merely exemplary and it is possible to change, add, andremove CCs using various other methods without being limited to themethod of Table 1.

Here, when a plurality of downlink CCs and/or a plurality of uplink CCsare configured for a UE and configuration information is changed, a CCis removed from the plurality of CCs, or a new CC is added to theplurality of CCs, there may be a problem associated with a connectionrelation between each CC unlike when one downlink CC and one uplink CCare configured for a UE.

This is described below with reference to FIG. 8.

FIG. 8 illustrates an exemplary connection relation between a single CCand a single CC in a carrier aggregation scheme and an exemplaryaddition of a downlink CC.

In the case of FIG. 8A, there is only one connection relation betweenuplink and downlink CCs since a single downlink CC and a single uplinkCC are configured for a UE. Generally, when a UE receives downlinksystem information of a CC, the UE can identify uplink information (forexample, uplink frequency information) of an uplink connected to thedownlink.

The connection relation of FIG. 8A can be considered as the connectionrelation by means of system information. Hereinafter, for ease ofexplanation, in drawings associated with embodiments of the presentinvention, a connection relation between an uplink and a downlink isshown by a dotted line when it is a connection relation by means ofsystem information.

Unlike the example of FIG. 8A, one downlink CC 810 is added in theexample of FIG. 8B. When a plurality of uplink CCs or a plurality ofdownlink CCs is configured for a UE, connection relations between theuplink and downlink CCs may be indefinite. For example, when aconnection relation between the added downlink CC 810 and the uplink CCis not clearly determined, there may be a problem in that it isdifficult to determine an uplink CC through which feedback informationfor data received through the added downlink CC 810 is to be transmittedto the eNB.

In addition, when a pre-set downlink CC is removed, there may also be aproblem in a method of communicating data through an uplink CC that hasbeen configured to be in a connection relation with the removed downlinkCC.

Accordingly, the present invention provides a method in which a downlinkCC and/or an uplink CC are changed, added, or deleted, a messageincluding identifier information specifying new connection relations isreceived, and data is communicated according to the identifierinformation included in the received message in a mobile communicationsystem that employs carrier aggregation.

Various embodiments of the present invention are described below indetail.

First, a method for modifying configuration of a plurality of CCs thathave been pre-set is described below with reference to FIG. 9.

FIG. 9 illustrates an example in which connection relations between CCsare changed through identifier information.

Before the configuration is changed, downlink CC 1 (911) is connected touplink CC 1 (912) and downlink CC 2 (921) is connected to uplink CC 2(922) to enable data communication.

At this time, a UE can receive a message including identifierinformation for modifying a connection relation between at least onedownlink CC and at least one CC from an eNB.

The message of FIG. 9 does not include CC addition or removalinformation and includes identifier information for modifying connectionrelations between existing CCs.

Upon receiving the message, the UE may configure a new connectionrelation based on the identifier information included in the receivedmessage, connect the downlink CC 1 (911) to the uplink CC 2 (922) andconnect the downlink CC 2 (921) to the uplink CC 1 (912) to enable datacommunication.

Namely, before the connection relations are changed through the message,the UE transmits corresponding feedback information to the eNB throughthe uplink CC 1 (912) upon receiving data through the downlink CC 1(911). However, after the connection relations are changed through themessage, the UE transmits the corresponding feedback information to theeNB through the uplink CC 2 (922).

The feedback information may be response data of the UE to data receivedfrom the eNB and may include feedback (HARQ ACK/NACK) of MAC layer.

Although the above description has been given with reference to the casein which feedback data for the received data is transmitted, the presentinvention is not limited thereto.

That is, not only when the UE transmits feedback data after receivingdata but also when the UE transmits preliminary information (forexample, channel status information, a precoding matrix index, a rankindicator, a scheduling request, or a reference signal) to the eNBbefore receiving data, modified connection relations between CCsindicated by identifier information included in a message may be appliedto perform communication.

It is also possible to add a new downlink CC through a message thatfurther includes information for adding a new downlink CC according toan embodiment of the present invention. In this case, identifierinformation included in the message includes information forconfiguration of a connection relation between an uplink CC and theadded downlink CC to enable data communication.

FIG. 10 illustrates an example in which a downlink CC is added and a newconnection relation is configured.

In the example of FIG. 10, a downlink CC may be added and a newconnection relation may be configured through a message and identifierinformation included in the message as shown in the following table.

TABLE 2 CC configuration message + Add CC3  − CC configuration   * DL CCconfiguration    >> DL CC specific configurations    >> UL Feedback CCidentifier = CC2

Feedback information for data received through downlink CC 3 (1013) thatis newly added as shown in Table 2 is transmitted to an eNB throughuplink CC 2 (1022).

However, Table 2 is merely exemplary and it is possible to add a CC andto configure a new connection relation using various other methodswithout being limited to the method of Table 2.

Meanwhile, an embodiment of the present invention provides a function toremove an existing downlink CC through a message that further includesdownlink CC removal information. Here, although an uplink CC that hasbeen connected to a downlink CC to be removed may cause a problem, thisproblem can be solved since identifier information included in themessage includes configuration information for a new connection relationof the uplink CC that has been connected to the downlink CC to beremoved.

FIG. 11 illustrates an example in which an existing downlink CC isremoved and a new connection relation is configured.

In the example of FIG. 11, a downlink CC may be removed and a newconnection relation may be configured through a message and identifierinformation included in the message as shown in the following table.

TABLE 3 CC configuration message + Release CC2  − CC identifier = CC2  −DL CC only release indication + Modify CC2  − CC configuration   * UL CCconfiguration    >> DL Feedback CC identifier = CC1

As shown in Table 3, downlink CC 2 (1121) is removed and uplink CC 2(1122) that has been connected to the downlink CC 2 (1121) is connectedto downlink CC 1 (1111) to enable data communication.

However, Table 3 is merely exemplary and it is possible to remove a CCand to configure a new connection relation using various other methodswithout being limited to the method of Table 3.

In addition, according to an embodiment of the present invention, it ispossible to add a new uplink CC through a message that further includesuplink CC addition information. In this case, identifier informationincluded in the message includes configuration information for aconnection relation between the added uplink CC and a downlink CC,thereby allowing data communication.

FIG. 12 illustrates an example in which an uplink CC is added and a newconnection relation is configured.

In the example of FIG. 12, an uplink CC may be added and a newconnection relation may be configured through a message and identifierinformation included in the message as shown in the following table.

TABLE 4 CC configuration message + Add CC2  − CC configuration   * UL CCconfiguration    >> UL CC specific configurations    >> DL Feedback CCidentifier = CC2

As shown in Table 4, feedback information for data transmitted throughuplink CC 2 (1222) that is newly added is received by a UE throughdownlink CC 1 (1211).

However, Table 4 is merely exemplary and it is possible to add a CC andto configure a new connection relation using various other methodswithout being limited to the method of Table 4.

In addition, according to an embodiment of the present invention, it ispossible to provide a function to change an existing connection relationthrough identifier information included in a message while adding anuplink CC.

FIG. 13 illustrates an example in which an uplink CC is added and aconnection relation between the added uplink CC and an existing downlinkCC is configured.

In the example of FIG. 13, an uplink CC may be added, a new connectionrelation may be configured, and an existing connection relation may bemodified through a message and identifier information included in themessage as shown in the following table.

TABLE 5 CC configuration message + Modify CC2  − CC configuration   * ULCC configuration    >> UL CC specific configurations    >> DL FeedbackCC identifier = CC2   * DL CC configuration    >> UL Feedback CCidentifier = CC2

As shown in Table 5, an existing connection relation configured betweendownlink CC 2 (1312) and an uplink CC 1 (1321) is changed and a newconnection relation is configured between newly added uplink CC 2 (1322)and downlink CC 2 (1321), thereby enabling data communication throughthe new connection relation.

However, Table 5 is merely exemplary and it is possible to add a CC andto configure a changed connection relation using various other methodswithout being limited to the method of Table 5.

Meanwhile, an embodiment of the present invention provides a function toremove an existing uplink CC through a message that further includesuplink CC removal information. Here, although a downlink CC that hasbeen connected to an uplink CC to be removed may cause a problem, thisproblem can be solved since identifier information included in themessage includes configuration information for a new connection relationof the downlink CC that has been connected to the uplink CC to beremoved.

FIG. 14 illustrates an example in which an existing uplink CC is removedand a new connection relation is configured.

In the example of FIG. 14, an uplink CC may be removed and a newconnection relation may be configured through a message and identifierinformation included in the message as shown in the following table.

TABLE 6 CC configuration message + Release CC2  − CC identifier = CC2  −UL CC only release indication + Modify CC2  − CC configuration   * DL CCconfiguration    >> UL Feedback CC identifier = CC1

As shown in Table 6, uplink CC 2 (1422) is removed and downlink CC 2(1421) that has been connected to the uplink CC 2 (1422) is connected touplink CC 1 (1412), thereby enabling data communication.

However, Table 6 is merely exemplary and it is possible to remove a CCand to configure a new connection relation using various other methodswithout being limited to the method of Table 6.

In addition, according to an embodiment of the present invention, it ispossible to add a new downlink CC and a new uplink CC through a messagethat further includes uplink CC and downlink CC addition information.

Here, identifier information included in the message may includeinformation indicating configuration of new connection relations betweenCCs including added downlink and uplink CCs, thereby enabling datacommunication.

FIG. 15 illustrates an example in which a downlink CC and an uplink CCare added and a new connection relation is configured.

As shown in FIG. 15, downlink CC 3 (1531) and uplink CC 3 (1532) may besimultaneously added through a message and a connection relation betweenthe added CCs may be configured.

Exemplary messages that may be applied in this case may include acombination of the messages of Table 2 and Table 5.

Accordingly, when a UE has received data through downlink CC 3 (1531),feedback information for the received data may be transmitted to an eNBthrough uplink CC 2 (1522).

Then, information regarding data that has been transmitted through theuplink CC 3 (1532) will be transmitted from the eNB through the downlinkCC 2 (1521).

Meanwhile, according to an embodiment of the present invention, it ispossible to remove an existing uplink CC while adding a new downlink CCthrough a message that further includes downlink CC addition informationand uplink CC removal information.

Here, identifier information included in the message may includeinformation indicating configuration of new connection relations of adownlink CC, which has been connected to an uplink CC that is to beremoved, and an added downlink CC.

FIG. 16 illustrates an example in which a downlink CC is added, anexisting uplink CC is removed, and a new connection relation isconfigured.

As shown in FIG. 16, new downlink CC 3 (1631) is added, uplink CC 2(1622) is removed, a connection relation between the added downlink CC 3(1631) and uplink CC 1 (1612) is configured through identifierinformation, and a new connection relation is configured between theuplink CC 1 (1612) and downlink CC 2 (1621) that has been in aconnection relation with the removed uplink CC 2 (1622).

Accordingly, feedback information for data received through the downlinkCC 2 (1621) or the downlink CC 3 (1631) may be transmitted to the eNBthrough the uplink CC 1 (1612) to perform communication.

In addition, it is possible to remove an existing downlink CC whileadding a new uplink CC through a message that further includes uplink CCaddition information and downlink CC removal information.

Here, identifier information included in the message may includeinformation indicating configuration of new connection relations of anuplink CC, which has been connected to a downlink CC that is to beremoved, and an added uplink CC.

FIG. 17 illustrates an example in which a downlink CC is removed, anexisting uplink CC is added, and a new connection relation isconfigured.

As shown in FIG. 17, new uplink CC 3 (1732) is added, downlink CC 2(1721) is removed, a connection relation between the added uplink CC 3(1732) and downlink CC 1 (1711) is configured through identifierinformation, and a new connection relation is configured between thedownlink CC 1 (1711) and uplink CC 2 (1722) that has been in aconnection relation with the removed downlink CC 2 (1721).

Accordingly, feedback information for data received through the uplinkCC 2 (1722) or the uplink CC 3 (1732) may be received by the UE throughthe downlink CC 1 (1711).

Meanwhile, according to an embodiment of the present invention, it ispossible to remove existing downlink and uplink CCs through a messagethat further includes downlink and uplink CC removal information.

Here, identifier information included in the message may includeinformation indicating configuration of new connection relations of anuplink CC and a downlink CC that have been connected to a downlink CCand an uplink CC that are to be removed, thereby enabling datacommunication.

For example, messages that are used to remove a downlink CC and anuplink CC may include a combination of the messages of Table 3 and Table5.

FIG. 18 illustrates an example in which an existing downlink CC and anexisting uplink CC are removed and a new connection relation isconfigured.

As shown in FIG. 18, downlink CC 3 (1831) and uplink CC 2 (1822) may beremoved through information included in a message and a new connectionrelation may be configured between uplink CC 3 (1832) that has beenconnected to the removed downlink CC 3 (1831) and downlink CC 2 (1822)that has been connected to the removed uplink CC 2 (1822), therebyperforming data communication.

Although a new connection relation is configured between CCs that havebeen in connection relations with removed CCs in the example of FIG. 18,this is merely exemplary and it is possible to configure a newconnection relation between other CCs without being limited to such CCsthat have been in connection relations with removed CCs.

In addition, although the above description has been given focusing on afunction to transmit feedback data in response to reception of data, thepresent invention is not limited to such a function.

That is, a modified connection relation between CCs indicated byidentifier information included in a message may be applied toperforming communication not only when feedback data is received afterdata is transmitted but also when a UE transmits preliminary information(for example, a power headroom report) for transmitting data to an eNB.

An example in which the present invention is applied to communication ofa power headroom report is described below.

First, the power headroom report generally indicates a differencebetween the amount of power that a UE can use for transmission on aspecific CC and the amount of power that a UE has already used fortransmission on the CC.

An eNB receives a power headroom report of a CC that is being used by aUE from the UE and calculates the amount of power that the UE is to usewhen performing transmission through the CC.

Here, to calculate power headroom for a specific CC, the UE measurespath loss of the CC and reflects the measured path loss in calculationof the power headroom.

Generally, the path loss of the CC is calculated by measuring a downlinkof a CC connected to an uplink of the CC through system information.

Accordingly, when the UE desires to calculate power headroom of anuplink of a specific CC for transmitting the CC through the uplink, theUE may specify a downlink CC whose path loss is to be measured andperform communication using the specified downlink CC, thereby applyingthe methods of the present invention.

Configuration of an association (or connection relation) suggested bythe present invention may not only be applied to clarifying a feedbackrelationship associated with data transmission and reception asdescribed above but may also be used for purposes described below.

First, the methods of the present invention may be applied toconfiguration of an association for transmitting/receiving a randomaccess message of a UE. Before this is described in detail, a randomaccess procedure that is provided by an LTE system is described belowwith reference to FIG. 19.

FIG. 19 illustrates a random access procedure to which the presentinvention may be applied.

First, FIG. 19A illustrates a contention-based random access procedure.

In the contention-based random access procedure, a UE randomly selectsone random access preamble from a random access preamble set indicatedthrough a handover command or system information, selects PRACHresources for transmitting the random access preamble, and transmits therandom access preamble through the selected PRACH resources.

After the UE transmits the random access preamble, the UE attempts toreceive a random access response destined for the UE within a randomaccess response reception window through a handover command or systeminformation transmitted by an eNB.

More specifically, the random access response information is transmittedin the form of a MAC PDU and the MAC PDU is transmitted through a PDSCH.In addition, a PDCCH is also transmitted to allow the UE to properlyreceive information transmitted through the PDSCH. That is, the PDCCHincludes information regarding the UE which is to receive the PDSCH,frequency and time information for radio resources of the PDSCH, atransmission format of the PDSCH, and the like.

Once the UE succeeds in receiving the PDCCH designated to the UE, the UEproperly receives a random access response through the PDSCH based oninformation of the PDCCH.

The random access response includes a random access preambleidentification (ID), a UL grant (associated with uplink radioresources), a temporary C-RNTI (temporary cell identifier), and a TimeAlignment Command (TAC) (including a time synchronization correctionvalue).

Since one random access response may include random access responseinformation for one or more UEs, the random access preamble ID needs tobe included in the random access response in order to indicate a UE forwhich the UL grant, the temporary C-RNTI, and the TAC are valid.

In the case that the UE has received a random access response which isvalid for the UE, the UE processes information items included in therandom access response.

That is, the UE applies the TAC and stores the temporary C-RNTI. Inaddition, the UE transmits data stored in a buffer or newly generateddata to the eNB.

Here, an identifier of the UE needs to be included in data of the ULgrant since, in the contention-based random access procedure, the eNBcannot determine which UEs perform the random access procedure and thusneeds to identify the UE in order to resolve contention at a later time.

In addition, the identifier of the UE may be included in the UL grantusing two methods. In the first method, when the UE has a valid cellidentifier which a corresponding cell has allocated to the UE before therandom access procedure, the UE transmits the cell identifier of the UEthrough the UL grant.

On the other hand, when no valid cell identifier has been allocated tothe UE before the random access procedure, the UE transmits dataincluding a unique identifier of the UE (for example, an S-TMSI or arandom Id). Generally, the unique identifier of the UE is longer thanthe cell identifier. When the UE has transmitted data through the ULgrant, the UE starts a contention resolution timer.

Here, the UE awaits an instruction from the eNB for contentionresolution after transmitting data including the identifier of the UEthrough the UL grant included in the random access response. That is,the UE attempts to receive a PDCCH for receiving a specific message.

The PDCCH may also be received using two methods. When the identifier ofthe UE transmitted through the UL grant is a cell identifier, the UEattempts to receive the PDCCH using the cell identifier of the UE. Onthe other hand, when the identifier is a unique identifier of the UE,the UE attempts to receive the PDCCH using a temporary C-RNTI includedin the random access response. Thereafter, in the former case, when theUE has received the PDCCH through the cell identifier of the UE beforethe contention resolution timer expires, the UE determines that therandom access procedure has been normally performed and terminates therandom access procedure.

In the latter case, when the UE has received the PDCCH through thetemporary cell identifier before the contention resolution timerexpires, the UE checks data carried in a PDSCH indicated by the PDCCH.If a unique identifier of the UE is included in the data carried in thePDSCH, the UE determines that the random access procedure has beennormally performed and terminates the random access procedure.

Next, FIG. 19B illustrates how a UE and an eNB operate in anon-contention-based random access procedure.

The non-contention-based random access procedure may be performed,first, when a handover procedure is performed and, second, when thenon-contention-based random access procedure is requested by aninstruction from an eNB. Of course, a contention-based random accessprocedure may also be performed in the two cases.

First, for the non-contention-based random access procedure, it isimportant to receive a designated random access preamble which is notlikely to cause collision (or contention). Methods of indicating therandom access preamble include using a handover command and using aPDCCH command.

After a random access preamble designated only for the UE is allocatedfrom the eNB, the UE transmits the random access preamble to the eNB.

Here, random access response information is received using the samemethod as in the contention-based random access procedure.

In addition, a detailed method for resolving contention in a randomaccess procedure is described below. Collision (or contention) occurs inthe random access procedure basically because the number of randomaccess preambles is limited.

That is, since the eNB cannot assign UE-specific random access preamblesto all UEs, the UE randomly selects and transmits a random accesspreamble among common random access preambles. Accordingly, two or moreUEs may select and transmit the same random access preamble through thesame PRACH resources. However, in this case, the eNB determines that onerandom access preamble has been transmitted from one UE.

Therefore, the eNB transmits a random access response to the UE andpredicts that the random access response will be received by one UE.However, contention may occur as described above such that two or moreUEs receive one random access response and thus each UE performsoperation based on the received random access response.

That is, there may be a problem in that two or more UEs transmitdifferent data through the same radio resources using one UL grantincluded in the random access response. Thus, all data may fail to betransmitted to the eNB, or the eNB may receive data of only a specificUE depending on the position or transmission power of each UE.

In the latter case, since the two or more UEs assume that they havesuccessfully transmitted their own data, the eNB needs to notify theUEs, which have failed in contention, of the information regardingfailure.

Notification of the information regarding failure or success is referredto as contention resolution. There are two contention resolutionmethods, one method using a Contention Resolution (CR) timer and theother method transmitting the identifier of the UE, which has succeededin contention, to the UEs.

The former method is used when the UE already has a unique cellidentifier (C-RNTI) before the random access procedure is performed.

That is, the UE which already has the cell identifier transmits dataincluding the cell identifier to the eNB in response to the randomaccess response and starts the CR timer. Then, when the UE has receivedPDCCH information including the cell identifier of the UE before the CRtimer expires, the UE determines that the UE has succeeded in contentionand normally terminates the random access procedure. On the other hand,when the UE has not received a PDCCH including the cell identifier ofthe UE before the CR timer expires, the UE determines that the UE hasfailed in contention and thus again performs the random access procedureor reports failure to a higher layer.

The latter contention resolution method, in which an identifier of a UEwhich has succeeded in contention resolution is transmitted, is usedwhen the UE has no unique cell identifier before the random accessprocedure. That is, when the UE has no cell identifier, the UE transmitsdata including a higher-level identifier (S-TMSI or random Id) than thecell identifier according to UL grant information included in the randomaccess response and starts a CR timer.

When data including the higher-level identifier of the UE has beenreceived before the CR timer expires, the UE determines that the randomaccess procedure has been successful. On the other hand, when dataincluding the higher-level identifier of the UE has not been receivedbefore the CR timer expires, the UE determines that the random accessprocedure has failed.

The methods suggested in this specification may be used to configure aconnection relation for random access of the UE.

For example, after a UE transmits a random access preamble throughuplink of a specific CC, the UE may designate a downlink CC throughwhich the UE expects to receive a random access response transmittedfrom the eNB as a response to the random access preamble. It ispreferable that a connection relation for random access be pre-set bythe eNB before the UE performs random access.

In addition, the methods of the present invention may be applied toconfigure a connection relation for time synchronization adjustment of aUE and an eNB.

Before describing how the present invention is applied to configure sucha connection relation, timing alignment maintenance of an uplink in theLTE system is described as follows.

In an LTE system, which is based on Orthogonal Frequency DivisionMultiplexing (OFDM) technology, data transmission of a specific UE maycause interference to communication with an eNB of other UEs. Tominimize such interference, the eNB needs to properly managetransmission timing of the UE.

More specifically, each UE may be present in any area in a cell. Thisindicates that the time required for data transmitted by each UE toarrive at an eNB may vary depending on the location of the UE. That is,the time required for data transmitted by a UE, which attemptstransmission at an edge of a cell, to arrive at the eNB will be longerthan the time required for data transmitted by a UE which is located atthe center of a cell to arrive at the eNB. That is, the time requiredfor data transmitted by a UE, which is located at the center of a cell,to arrive at the eNB will be shorter than the time required for datatransmitted by a UE which is located at an edge of a cell to arrive atthe eNB.

An eNB needs to perform management to allow data or signals transmittedby all UEs in a cell to be received within every time boundary in orderto prevent the influence of interference. Therefore, the eNB needs toappropriately control transmission timing of each UE according to theposition or situation of the UE. Such transmission timing control isreferred to as time synchronization management.

One method of managing time synchronization may be a random accessoperation. That is, the eNB receives a random access preambletransmitted by a UE through a random access procedure and calculates atime synchronization value associated with transmission timing usingreceived information of the random access preamble.

The eNB then notifies the UE of the calculated time synchronizationvalue through a random access response and the UE then updatestransmission timing using the calculated time synchronization value. Inanother method, the eNB receives a sounding reference signal that the UEperiodically or randomly transmits, and calculates a timesynchronization value of the UE through the received signal and thennotifies the UE of the calculated time synchronization value.

Accordingly, the eNB instructs the UE to finely control uplinktransmission timing in order to allow the UE to transmit data at acorrect timing through a specific uplink such that the UE and the eNBcan maintain correct synchronization.

This instruction is referred to as timing advance in LTE. Through timingadvance, it is possible to slightly delay or advance the uplinktransmission timing of the UE. The UE applies a received timing advancevalue in the form of an offset with respect to used downlink carriertiming and determines uplink timing.

Returning to the description of the method of the present invention,when the UE determines transmission timing through a specific uplink CC,the eNB may designate a downlink CC that the UE needs to use as areference. Here, it is preferable that a connection relation of the UEand the eNB for time synchronization is pre-set by the eNB before the UEperforms random access.

The following is a description of a UE and an eNB for modifying aconnection relation between CCs for data communication of the UEaccording to another aspect of the present invention.

FIG. 20 illustrates a configuration of an embodiment of a wirelesscommunication system including a UE and an eNB according to the presentinvention.

As shown in FIG. 20, the UE may include a receiving module 2011, atransmitting module 2012, a processor 2013, and a memory 2014. Thereceiving module 2011 may receive various signals, data, information,etc., from the eNB or the like. The transmitting module 2012 maytransmit various signals, data, information, etc., to the eNB or thelike. The processor 2013 may control communication of data through amessage received through the receiving module 2011. The UE may beconfigured such that, when the UE receives a message includingidentifier information for modifying a connection relation betweendownlink and uplink CCs from the eNB through the receiving module andreceives specific data through the downlink CC, the UE transmitsfeedback information for the received data to the eNB through thetransmitting module using the uplink CC modified based on the identifierinformation.

Meanwhile, the eNB may include a receiving module 2031, a transmittingmodule 2032, a processor 2033, and a memory 2034. The receiving module2031 may receive various signals, data, information, etc., from the UEor the like. The transmitting module 2032 may transmit various signals,data, information, etc., to the UE or the like.

The processor 2033 may perform a control operation to transmitconfiguration information of a specific CC among a plurality of CCs tothe UE through the transmitting module 2032. In addition, the processor2033 performs arithmetic processing on information received by the UE,information to be transmitted to the outside, or the like and the memory2034 may store the arithmetic-processed information or the like for acertain time and may be replaced with a component such as a buffer (notshown).

The following is a detailed description of configurations of theprocessors of the UE and the eNB, which are core components of the UEand the eNB.

FIG. 21 illustrates functions (especially, associated with a structureof an L2 (second) layer) of the processor of the eNB to which theembodiments of the present invention are applied and FIG. 22 illustratesfunctions (especially, associated with a structure of an L2 (second)layer) of the processor of the UE to which the embodiments of thepresent invention are applied.

A PDCP layer 2110, an RLC layer 2120, and a MAC layer 2130 areillustrated in a downlink L2 structure 2100 shown in FIG. 21. In FIG.21, elements 2105, 2115, 2125, and 2135 denoted by circles on interfacesbetween the layers represent Service Access Points (SAP) forpear-to-pear communication. The SAP between a PHY channel (not shown)and the MAC layer provides a transport channel as denoted by “2135” andthe SAP between the MAC layer and the RLC layer provides a logicalchannel as denoted by “2125”. General operations of the layers are thesame as described above.

The MAC layer multiplexes a plurality of logical channels (i.e., radiobearers) from the RLC layer. In the downlink L2 structure, a pluralityof multiplexing entities 2131 of the MAC layer are associated withMultiple Input Multiple Output (MIMO) technology. In a system wherecarrier aggregation (CA) technology is not taken into consideration, inthe case of non-MIMO, multiple logical channels are multiplexed togenerate one transport channel and therefore one Hybrid Automatic Repeatand reQuest (HARQ) Entity (not shown) is provided for one multiplexingentity 2131.

On the other hand, the processor of the eNB where CA technology is takeninto consideration generates a plurality of transport channelscorresponding to a plurality of CCs from one multiplexing entity 2131.In this regard, in CA technology, one HARQ entity 2032 manages one CC.Accordingly, in the MAC layer 2130 of the processor of the eNB thatsupports CA technology, a plurality of HARQ entities 2132 are providedfor one multiplexing entity 2131 and operations associated with theplurality of HARQ entities 2132 are performed in the MAC layer 2130. Inaddition, since each HARQ entity 2132 independently processes atransport block, it is possible to simultaneously transmit and receive aplurality of transport blocks through a plurality of CCs.

The uplink L2 structure 2200 of FIG. 22, i.e., the L2 structure of theprocessor of the UE, performs the same operations as the downlink L2structure 2100 of FIG. 21 except that one multiplexing entity 2231 isincluded in one MAC layer 2230. That is, a plurality of HARQ entities2232 are provided for a plurality of CCs, operations associated with aplurality of HARQ entities 2232 are performed in the MAC layer 2230, anda plurality of transport blocks can be simultaneously transmitted andreceived through a plurality of CCs.

The embodiments of the present invention described above may beimplemented by various means. For example, the embodiments of thepresent invention may be implemented by hardware, firmware, software, orany combination thereof.

In the case in which the present invention is implemented with hardware,the methods according to the embodiments of the present invention may beimplemented with one or more application specific integrated circuits(ASICs), digital signal processors (DSPs), digital signal processingdevices (DSPDs), programmable logic devices (PLDs), field programmablegate arrays (FPGAs), processors, controllers, microcontrollers,microprocessors, or the like.

Although the present invention has been described above with referenceto each of the embodiments, it will be understood by a person havingordinary skills in the art that the embodiments may be combined invarious ways to be practiced. Thus, it should be understood that thepresent invention includes all embodiments within the scope of theappended claims without being limited to the above embodiments.

INDUSTRIAL APPLICABILITY

Although each of the embodiments of the present invention has beendescribed focusing on the case in which the present invention is appliedto a mobile communication system that is based on 3GPP LTE for ease ofexplanation, the present invention can be applied in the same manner tovarious other mobile communication systems in which a measurementoperation for mobility management of a UE is used and a UE cansimultaneously use a plurality of CCs.

1-14. (canceled)
 15. A method for configuring component carriers at acommunication device in a wireless communication system supportingcarrier aggregation, the method comprising: receiving, by thecommunication device, a message including configuration information fora first component carrier; and modifying, by the communication device,configuration of the component carriers according to the configurationinformation, wherein the configuration information includesidentification information indicating a second component carrier, andwherein the first component carrier is associated with the secondcomponent carrier according to the identification information.
 16. Themethod of claim 15, wherein the message includes information forreconfiguring radio resource control (RRC) connection of the userequipment.
 17. The method of claim 15, wherein downlink of the firstcomponent carrier is associated with uplink of the second componentcarrier.
 18. The method of claim 15, wherein uplink of the firstcomponent carrier is associated with downlink of the second componentcarrier.
 19. The method of claim 15, further comprising: measuring, bythe communication device, a path loss in downlink of the secondcomponent carrier; and transmitting, by the communication device, powerheadroom information for uplink transmission on the first componentcarrier based on the measured path loss.
 20. The method of claim 19,wherein the power headroom information is obtained using the measuredpath loss.
 21. The method of claim 19, wherein the power headroominformation is obtained from a difference between a maximum transmissionpower for the first component carrier and an estimated transmissionpower for the first component carrier.
 22. A communication deviceconfigured to configure component carriers in a wireless communicationsystem supporting carrier aggregation, the communication devicecomprising: a receiving module; and a processor configured to: controlthe receiving module to receive a message including configurationinformation for a first component carrier, and modify configuration ofthe component carriers according to the configuration information,wherein the configuration information includes identificationinformation indicating a second component carrier, and wherein the firstcomponent carrier is associated with the second component carrieraccording to the identification information.
 23. The communicationdevice of claim 22, wherein the message includes information forreconfiguring radio resource control (RRC) connection of the userequipment.
 24. The communication device of claim 22, wherein downlink ofthe first component carrier is associated with uplink of the secondcomponent carrier.
 25. The communication device of claim 22, whereinuplink of the first component carrier is associated with downlink of thesecond component carrier.
 26. The communication device of claim 22,further comprising: a transmission module, wherein a processor isfurther configured to: measure a path loss in downlink of the secondcomponent carrier, and control the transmission module to transmit powerheadroom information for uplink transmission on the first componentcarrier based on the measured path loss.
 27. The communication device ofclaim 26, wherein the power headroom information is obtained using themeasured path loss.
 28. The communication device of claim 26, whereinthe power headroom information is obtained from a difference between amaximum transmission power for the first component carrier and anestimated transmission power for the first component carrier.